Use force=True when PrintOn/PrintOff combination is used

Rosen Matevrequested to merge
rmatev-improve-python-logging into 2017-patches

PrintOff() following PrintOn() does not always restore print level as, per default, PrintOn() will not decrease LogFilter.printing_level if it is already 0 (see here). However, PrintOff() will increase it unconditionally. The fix (without touching Gaudi) is to use PrintOn(force=True).

Also removed some lone PrintOff()s.

This does not change the stdout of Brunel.2017magup.

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